Tagraxofusp, a first-in-class CD123-targeted agent: Five-year postapproval comprehensive review of the literature.

Tagraxofusp is a first-in-class CD123-directed conjugate of an amended diphtheria toxin platform and recombinant interleukin 3. Binding and subsequent internalization of the drug result in cell death via disruption of intracellular protein synthesis. CD123 is a surface marker that is expressed in several hematological malignancies, especially blastic plasmacytoid dendritic cell neoplasm (BPDCN), where its expression is ubiquitous. A pivotal study of tagraxofusp in BPDCN resulted in its approval for the treatment of BPDCN, the first treatment approved for this indication. Since the introduction of tagraxofusp, research has focused on the management of adverse effects, combination therapy to improve outcomes in fit patients, and dosing and combination strategies to mitigate toxicities while preserving efficacy, especially among older patients. The successful targeting of CD123 in BPDCN has also encouraged research into a variety of other CD123-positive hematological neoplasms, including acute myeloid leukemia (AML), and informed the development of other novel agents targeting CD123. This review examines the clinical data leading to the development and approval of tagraxofusp in BPDCN, how it is being used in combination to improve outcomes in BPDCN and AML, and its developing role in other hematological malignancies.

Tagraxofusp in myeloid malignancies.

Tagraxofusp (or SL-401) is a recombinant molecule composed of human interleukin-3 that binds CD123 on neoplastic cells fused to a truncated diphtheria toxin (DT). Tagraxofusp's most significant success has come from studies involving patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN), an aggressive disease that is usually refractory to conventional chemotherapy. Tagraxofusp had an acceptable safety profile and high efficacy in early phase I/II studies on patients with BPDCN. Another phase II study confirmed the good response rates, resulting in Food and Drugs Administration and European Medicine Agency approval of tagraxofusp for the treatment of BPDCN. Considering its high efficacy and its manageable safety profile, tagraxofusp has been suddenly explored in other myeloid malignancies with high expression of cell surface CD123, both in monotherapy or combination strategies. The triplet tagraxofusp-azacytidine-venetoclax appears to be of particular interest among these combinations. Furthermore, combination strategies may be used to overcome tagraxofusp resistance. The downregulation of DPH1 (diphthamide biosynthesis 1), the enzyme responsible for the conversion of histidine 715 on eEF2 to diphthamide, which is then the direct target of ADP ribosylation DT, is typically associated with this resistance phenomenon. It has been discovered that azacitidine can reverse DHP1 expression and restore sensitivity to tagraxofusp. In conclusion, the success of tagraxofusp in BPDCN paved the way for its application even in other CD123-positive malignancies. Nowadays, several ongoing trials are exploring the use of tagraxofusp in different myeloid neoplasms. This review aims to summarize the actual role of tagraxofusp in BPDCN and other CD123-positive myeloid malignancies.

Diagnostic management of blastic plasmacytoid dendritic cell neoplasm (BPDCN) in close interaction with therapeutic considerations.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), a rare malignancy derived from plasmacytoid dendritic cells, can mimic both acute leukemia and aggressive T-cell lymphoma. Therapy of this highly aggressive hematological disease should be initiated as soon as possible, especially in light of novel targeted therapies that have become available. However, differential diagnosis of BPDCN remains challenging. This retrospective study aimed to highlight the challenges to timely diagnoses of BPDCN. We documented the diagnostic and clinical features of 43 BPDCN patients diagnosed at five academic hospitals from 2001-2022. The frequency of BPDCN diagnosis compared to AML was 1:197 cases. The median interval from the first documented clinical manifestation to diagnosis of BPDCN was 3 months. Skin (65%) followed by bone marrow (51%) and blood (45%) involvement represented the most common sites. Immunophenotyping revealed CD4 + , CD45 + , CD56 + , CD123 + , HLA-DR + , and TCL-1 + as the most common surface markers. Overall, 86% (e.g. CD33) and 83% (e.g., CD7) showed co-expression of myeloid and T-cell markers, respectively. In the median, we detected five genomic alterations per case including mutational subtypes typically involved in AML: DNA methylation (70%), signal transduction (46%), splicing factors (38%), chromatin modification (32%), transcription factors (32%), and RAS pathway (30%), respectively. The contribution of patients (30%) proceeding to any form of upfront stem cell transplantation (SCT; autologous or allogeneic) was almost equal resulting in beneficial overall survival rates in those undergoing allogeneic SCT (p = 0.0001). BPDCN is a rare and challenging entity sharing various typical characteristics of other hematological diseases. Comprehensive diagnostics should be initiated timely to ensure appropriate treatment strategies.

Multiple Genomic Alterations, Including a Novel AFF4::IRF1 Fusion Gene, in a Treatment-Refractory Blastic Plasmacytoid Dendritic-Cell Neoplasm: A Case Report and Literature Review.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with an aggressive clinical course and poor prognosis. The genetic abnormalities in BPDCN are heterogeneous; therefore, its molecular pathogenesis and the prognostic importance of genomic alterations associated with the disease are not well defined. Here we report a case of BPDCN with a novel AFF4::IRF1 fusion predicted to lead to a loss-of-function of the IRF1 tumor suppressor, somatic mutations of ASXL1, TET2, and MYD88, as well as multiple intrachromosomal deletions. The patient showed resistance to Tagraxofusp and Venetoclax, and he died about 16 months after diagnosis. Considering the predicted effect of the AFF4::IRF1 fusion on IRF1's antitumor effects and immune regulation, and the possibility of its relevance to the aggressive course observed in this case, we propose further evaluation of the clinical significance of this fusion in BPDCN in future cooperative group studies and the consideration of therapeutic strategies aimed at restoring IRF1-dependent antineoplastic effects in such cases.

Tagraxofusp followed by combined azacitidine and venetoclax in blastic plasmacytoid dendritic cell neoplasm: A case report and literature review.

INTRODUCTION: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic malignancy that originates from plasmacytoid dendritic cells. It can involve skin, bone marrow, and/or lymph nodes. There is no consensus recommendation regarding treatment especially in the relapsed setting. Tagraxofusp, a CD123 directed agent, was recently approved by the Food and Drug Administration to treat BPDCN. We report a case of an elderly patient with diagnosis of BPDCN who was treated initially with tagraxofusp followed by azacitidine and venetoclax combination on relapse. CASE REPORT: A 79 year old male presented with violaceous skin lesions. He had no other symptoms. Biopsy of these lesions was consistent with a diagnosis of BPDCN. Further testing showed no extracutaneous involvement.Management and outcome: Tagraxofusp was started at full dose (12 mcg/kg). This dose was not tolerated well. Patient could only tolerate the lowest dose (5 mcg/kg). Toxicities included elevated liver function tests, hyperglycemia, capillary leak syndrome, and pancreatitis. Dose escalation on progression was not possible due to side effects. Treatment was switched to venetoclax and azacitidine. Combination treatment was tolerated very well and patient showed major cutaneous response after 5 cycles and continues to do well. DISCUSSION: Tagraxofusp is a novel therapy that needs more real-world experience. This case describes the clinical course of an elderly patient on tagraxofusp. We also review the literature of azacytidine/venetoclax combination as a potential yet tolerable treatment option for this rare disease entity. This is the fourth case in literature to be treated with this combination.

Recent Advances in the Biology and CD123-Directed Treatment of Blastic Plasmacytoid Dendritic Cell Neoplasm.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive myeloid malignancy of the dendritic cell lineage that affects patients of all ages, though the incidence appears to be highest in patients over the age of 60 years. Diagnosis is based on the presence of plasmacytoid dendritic cell precursors expressing CD123, the interleukin-3 (IL-3) receptor alpha, and a distinct histologic appearance. Timely diagnosis remains a challenge, due to lack of disease awareness and overlapping biologic and clinical features with other hematologic malignancies. Prognosis is poor with a median overall survival of 8 to 14 months, irrespective of disease presentation pattern. Historically, the principal treatment was remission induction therapy followed by a stem cell transplant (SCT) in eligible patients. However, bridging to SCT is often not achieved with induction chemotherapy regimens. The discovery that CD123 is universally expressed in BPDCN and is considered to have a pathogenetic role in its development paved the way for the successful introduction of tagraxofusp, a recombinant human IL-3 fused to a truncated diphtheria toxin payload, as an initial treatment for BPDCN. Tagraxofusp was approved in 2018 by the United States Food and Drug Administration for the treatment of patients aged 2 years and older with newly diagnosed and relapsed/refractory BPDCN, and by the European Medicines Agency in 2021 for first-line treatment of adults. The advent of tagraxofusp has opened a new era of precision oncology in the treatment of BPDCN. Herein, we present an overview of BPDCN biology, its diagnosis, and treatment options, illustrated by clinical cases.

Real-world evidence on tagraxofusp for blastic plasmacytoid dendritic cell neoplasm - collected cases from a single center and case reports.

Introduction: Blastic plasmacytoid dendritic cell neoplasia (BPDCN) is a rare, aggressive hematologic malignancy. Until recently, the only curative treatment consisted of intensive chemotherapy, followed by hematopoietic cell transplantation (HCT) in eligible adult cases. Tagraxofusp, a CD123-targeted protein-drug conjugate and the first approved targeted treatment for BPDCN, might enhance outcomes especially in patients not eligible for intensive therapies. Methods: Here, we report real-world outcomes of five male patients with a median age of 79 years who received tagraxofusp as first-line treatment for BPDCN. Results: Tagraxofusp was found to be well-tolerated in this elderly cohort, with only one patient requiring discontinuation. Three patients responded to the treatment (two patients achieved a CR and one patient achieved a partial response), of which two subsequently underwent allogeneic (allo) HCT. One patient is alive and well after ≥ 4 years after alloHCT, and one patient shows sustained CR after now 13 cycles of tagraxofusp. The other three patients died of progressive disease 4-11 months after initiation of treatment. Discussion: In line with results from 13 published cases outside clinical trials in the literature, sustained responses were associated with CR after tagraxofusp treatment and subsequent alloHCT. Our results provide real-world evidence for safety and efficacy of tagraxofusp as first-line treatment for BPDCN.

Blastic Plasmacytoid Dendritic Cell Neoplasm: A Comprehensive Review of the Disease, Central Nervous System Presentations, and Treatment Strategies.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematologic malignancy with poor outcomes. The World Health Organization (WHO) redefined BDCN as a distinct disease entity in 2016. BPDCN arises from plasmacytoid dendritic cells, manifesting primarily in the skin, bone marrow, and lymph nodes, occasionally involving the central nervous system (CNS). This presents challenges in diagnosis and treatment, with CNS involvement often overlooked in standard diagnostic workups due to BPDCN's rarity and patients often being neurologically asymptomatic at diagnosis. CNS involvement typically emerges during relapse, yet clinical trials often exclude such cases, limiting our understanding of its development and treatment. Treatment options for CNS involvement include intrathecal (IT) chemotherapies like methotrexate and cytarabine, often in combination with systemic agents. Tagraxofusp and traditional regimens for acute myeloid leukemia show limited success at preventing CNS relapse, prompting exploration of combined therapies like hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (HyperCVAD) with venetoclax and adding IT chemotherapy to other backbones. Ongoing clinical trials investigating emerging therapies offer hope despite limited focus on CNS implications. Trials incorporating CNS-involved patients aim to pioneer novel treatment approaches, potentially reshaping BPDCN management. Understanding CNS involvement's complexities in BPDCN remains crucial for tailored treatments and better patient outcomes.

Efficacy and manageable safety of tagraxofusp in blastic plasmacytoid dendritic cell neoplasm: a case series of pediatric and adolescent/young adult patients.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) predominantly occurs in adults ≥60 years old; 10-20% of cases are pediatric or adolescent/young adult (AYA) patients. Tagraxofusp (TAG, Elzonris®) is the only approved treatment for BPDCN; in the United States it is approved for patients aged ≥2 years. Data on treating pediatric and AYA BPDCN patients are limited. We present a case series of pediatric and AYA patients with BPDCN treated with TAG. Eight patients (five newly diagnosed; three relapsed/refractory [R/R]), aged 2-21 years, received 12 mcg/kg TAG. Seven patients were female; most had skin (n = 6) and/or bone marrow (n = 4) involvement. No new safety signals were identified. Grade 3 adverse events were headache (n = 1) and transaminitis (n = 2). Three patients with newly diagnosed BPDCN achieved complete response, one achieved partial response, and one had stable disease (SD). One patient with R/R BPDCN achieved a minor response; one had SD. Seven patients (88%) were bridged to stem cell transplant: 80% of newly diagnosed patients and 100% of R/R patients. Five patients remained alive at last follow-up. These cases highlight the efficacy and safety of TAG in pediatric and AYA patients for whom there is no other approved BPDCN therapy.

Treatment of patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN): focus on the use of tagraxofusp and clinical considerations.

BPDCN is an aggressive myeloid malignancy with a poor prognosis. It derives from the precursors of plasmacytoid dendritic cells and is characterized by CD123 overexpression, which is seen in all patients with BPDCN. The CD123-directed therapy tagraxofusp is the only approved treatment for BPDCN; it was approved in the US as monotherapy for the treatment of patients aged ≥2 years with treatment-naive or relapsed/refractory BPDCN. Herein, we review the available data supporting the utility of tagraxofusp in treating patients with BPDCN. In addition, we present best practices and real-world insights from clinicians in academic and community settings in the US on how they use tagraxofusp to treat BPDCN. Several case studies illustrate the efficacy of tagraxofusp and discuss its safety profile, as well as the prevention, mitigation, and management of anticipated adverse events.

[Blastic plasmacytoid dendritic cell neoplasm (BPDCN) : A rare hematologic neoplasm with frequent cutaneous involvement]. / Blastische plasmazytoide dendritische Zellneoplasie (BPDCN) : Eine seltene hämatologische Neoplasie mit häufiger kutaner Beteiligung.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy that derives from precursors of plasmacytoid dendritic cells and is characterized by disseminated, erythematous or bluish-livid plaques or nodi. Because of the disease's rarity the diagnosis and treatment still pose a significant challenge. We present a case of a patient with BPDCN and show clinical and diagnostic characteristics as well as potential treatment regimes.

Blastic Plasmacytoid Dendritic Cell Neoplasm Presenting as a Mammary Gland Tumor in a Pediatric Patient: A Case Report.

Emanating from a discrete category within the lympho-hematopoietic tumor system, as established by the World Health Organization in 2008, the blastic plasmacytoid dendritic cell neoplasm constitutes an uncommon malignant hematological disorder. It is routinely misidentified on account of its conspicuous dermatological manifestation, yet may insidiously permeate bone marrow and lymph nodes, involving peripheral blood and diverse extra-nodal tissues. Instances of mammary gland encroachment are extraordinarily infrequent. The current document delineates a case of a 14-year-old female patient contending with blastic plasmacytoid dendritic cell neoplasm, whose primary symptom was a mammary nodule, and whose breast and bone marrow/blood involvement were synchronous, in attempt to increase clinical vigilance.

Histopathological Markers for Target Therapies in Primary Cutaneous Lymphomas.

In recent years, targeted (biological) therapies have become available also for primary cutaneous T-cell lymphomas (PCTCLs) including anti-CD30 (brentuximab vedotin) in mycosis fungoides, primary cutaneous anaplastic large T-cell lymphoma, lymphomatoid papulosis; anti-CCR4 (mogamulizumab) in Sezary syndrome; anti-CD123 (tagraxofusp) in blastic plasmocytoid cell neoplasm. Moreover, anti-PD1 (nivolumab), anti-PDL1 (pembrolizumab, atezolizumab), anti-CD52 (alemtuzumab), anti-KIR3DL2-CD158k (lacutamab), and anti-CD70 (cusatuzumab) have been tested or are under investigations in phase II trials. The expression of these epitopes on neoplastic cells in skin biopsies or blood samples plays a central role in the management of PCTCL patients. This narrative review aims to provide readers with an update on the latest advances in the newest therapeutic options for PCTCLs.

Clinical Insights into the Management of Blastic Plasmacytoid Dendritic Cell Neoplasm.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is aggressive hematologic malignancy derived from plasmacytoid dendritic cell precursors of myeloid cell lineage. Patients frequently present with bruise-like skin lesions, which typically are followed months later by progressive cytopenias. Historically, BPDCN prognosis has been dismal, with median overall survival ranging from 9 to 13 months. In the past 2 decades, our understanding of BPDCN pathogenesis has led to the successful development of novel therapeutics. In December 2018, the FDA approved tagraxofusp-erzs for adults and pediatric patients older than 2 years who have either treatment-naïve or relapsed/refractory BPDCN. Acute lymphoblastic leukemia (ALL)-based chemotherapy regimens also provide comparable outcomes to tagraxofusp. In our practice, for patients with good performance status, we use tagraxofusp, ALL-based chemotherapy regimens, or clinical trials as frontline induction therapy, followed by consolidation with allogeneic stem cell transplant once the first complete response has been achieved. Our induction regimen also includes intrathecal chemotherapy for central nervous system prophylaxis. Patients with poor performance status who are treatment-naïve or patients with relapsed/refractory disease have limited therapeutic options, and we strongly recommend enrollment in clinical trials; several novel agents and combinations are currently under clinical investigation for both treatment-naïve and relapsed/refractory BPDCN.

Evaluating tagraxofusp for the treatment of blastic plasmacytoid dendritic cell neoplasm (BPDCN).

INTRODUCTION: Unique among hematologic malignancies, blastic plasmacytoid dendritic cell neoplasm (BPDCN) affects multiple compartments including bone marrow, hematologic, lymphatic, dermatologic, and central nervous systems (CNS). Treating BPDCN is challenging, historically, as patients display refractoriness to chemotherapy and absence of long-term remissions in many cases not treated with hematopoietic stem cell transplantation. Discovering the prevalent overexpression of surface receptor CD123 (IL3-Rα) on BPDCN cells led to development of tagraxofusp, a novel anti-CD123 agent for patients with BPDCN. AREAS COVERED: Herein, the authors discuss the preclinical development and phase I/II clinical studies, which led to the approval of tagraxofusp. They discuss the current treatment landscape of BPDCN with tagraxofusp alone or combined with chemotherapy and highlight several ongoing clinical trials involving combinations of tagraxofusp with novel targeted therapeutics for BPDCN. EXPERT OPINION: Tagraxofusp has significantly improved the treatment landscape for patients with newly diagnosed BPDCN and has led to investigative efforts and augmentation of various strategies of targeting CD123, such as antibody-drug conjugates and anti-CD123 chimeric antigen receptor T-cells. However, relapsed/refractory disease and CNS-involvement of BPDCN remain therapeutic challenges. The authors recommend that healthcare providers consider multiple-agent clinical trial approaches and adequate CNS-prophylaxis for all patients with BPDCN.

Venetoclax and Azacitidine in the Treatment of Blastic Plasmacytoid Dendritic Cell Neoplasm Refractory to Conventional Therapy.

Blastic plasmacytoid dendritic cell neoplasm is a rare and aggressive hematological malignancy associated with poor prognosis and limited treatment options. No guideline-directed therapy existed until the approval of tagraxofusp in 2018 by the Food and Drug Administration. Multiple clinical trials are undergoing as treatment options continue to evolve. We report a case refractory to tagraxofusp and pivekimab sunirine with subsequent remission achieved on venetoclax and azacitidine therapy.

Foot gangrene following Tagraxofusp treatment for blastic plasmacytoid dendritic cell neoplasm: Case report.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic malignancy. It is associated with poor prognosis and heterogenous presentation. The CD123-directed cytotoxin, Tagraxofusp, is a targeted therapy for BPDCN. Here, we report an 81-year-old female diagnosed with BPDCN. The patient was treated with Tagraxofusp and underwent a remarkably long remission (>20 months) without stem-cell transplantation. She, however, experienced blue toe syndrome and left foot gangrene. We postulate that these previously unreported side effects were caused by microembolization. Characterization of the incidence of thrombo- and microembolizations in such a context, as well as prophylactic management options, are warranted.

CD123 and More: How to Target the Cell Surface of Blastic Plasmacytoid Dendritic Cell Neoplasm.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive leukemia derived from plasmacytoid dendritic cells (pDCs). It is associated with a remarkably poor prognosis and unmet need for better therapies. Recently, the first-in-class CD123-targeting therapy, tagraxofusp, was approved for treatment of BPDCN. Other CD123-targeting strategies are in development, including bispecific antibodies and combination approaches with tagraxofusp and other novel agents. In other blood cancers, adoptive T-cell therapy using chimeric antigen receptor (CAR)-modified T cells represents a promising new avenue in immunotherapy, showing durable remissions in some relapsed hematologic malignancies. Here, we report on novel and innovative therapies in development to target surface molecules in BPDCN currently in clinical trials or in preclinical stages. We also discuss new cell surface targets that may have implications for future BPDCN treatment.

Blastic plasmacytoid dendritic-cell neoplasia: a challenging case report.

Blastic plasmacytoid dendritic-cell neoplasm (BPDCN) is an extremely rare disease that originates from dendritic cells and is associated with a poor overall survival (OS). Diagnostic and therapeutic standards are less well-established in comparison to other leukemic conditions and standards of care are lacking. Morphologic and molecular similarities to acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML) are hard to distinguish. We here report a BPDCN patient with a long, challenging diagnostic period. While bone marrow biopsies initially failed to prove the correct diagnosis, a cutaneous biopsy finally identified a CD45+/CD56+/CD4+/CD123+/CD33+/MPO- population suggestive of BPDCN which was confirmed by flow cytometry. Molecular analysis revealed an ASXL-1, TET2 and SRSF2-mutation, cytogenetic analysis showed a normal karyotype. Treatment with the recently approved CD123-cytotoxin Tagraxofusp showed initially a very good response. This case reflects diagnostic and therapeutic difficulties in BPDCN as very rare, easily misdiagnosed neoplasia and the need for precise diagnostic care.

Relapse of tagraxofusp treated blastic plasmacytoid dendritic cell neoplasm with loss of CD123 expression.

Tagraxofusp, a CD123-based-targeted immunotherapy, was recently approved to treat blastic plasmacytoid dendritic cell neoplasm (BPDCN) with excellent response. Also, a subset of BPDCN shows resistance to tagraxofusp. These resistant cases continue to express CD123, which forms the basis of the continued utility of tagraxofusp in newer combination chemotherapies to overcome resistance in BPDCN. Herein, we report a case of an elderly male with BPDCN that achieved complete remission on initial primary treatment with tagraxofusp. However, BPDCN relapsed after 1.5 years while on treatment, with loss of CD123 expression. At relapse, the neoplasm was comprehensively immunophenotyped by flow cytometry (performed on both peripheral blood and bone marrow specimen) and by immunohistochemical evaluation of the bone marrow clot section. The neoplasm at relapse was diagnostic of BPDCN with a lack of CD123 expression. This case highlights a potential limitation of current and upcoming tagraxofusp-based multidrug therapies, at least in a subset of refractory BPDCN. We believe our report will serve as a sentinel to incite future investigations involving alternate resistance mechanisms in BDPCN.